1) The CSD might end up reading the VDD instead of the VDDA in this case, as it is essentially reading the power rails to filter out noise, and the power rails would be switched to be VDD instead of VDDA. A cypress employee might know more specifically.

2) I would say the VDDA is connected to the VDD internally, not the VCCD. The main difference on the VCCD is the voltage regulator tying it to 1.8v. Using the CSD on that pin definitely would NOT work, as the CSD needs the noisy power pin to filter the power noise.